Rate Matters (Details) - USD ($)
$ in Millions |
1 Months Ended |
9 Months Ended |
12 Months Ended |
Oct. 31, 2017 |
Aug. 31, 2017 |
Nov. 30, 2016 |
Sep. 30, 2017 |
Dec. 31, 2015 |
Dec. 31, 2014 |
| PUCT Proceeding - Appeal of the Texas 2015 Electric Rate Case Decision |
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| Public Utilities, General Disclosures [Line Items] |
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| Public Utilities, Requested Rate Increase (Decrease), Amount |
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$ 42.1
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| PUCT Proceeding - Texas 2017 Electric Rate Case |
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| Public Utilities, General Disclosures [Line Items] |
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| Public Utilities, Requested Rate Increase (Decrease), Amount |
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$ 66.4
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| Public Utilities, Requested Rate Increase (Decrease), Percentage |
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7.10%
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| Public Utilities, Number of Months in Test Year |
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12 months
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| Public Utilities, Number of Months in Test Year which are Estimated |
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3 months
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| Public Utilities, Requested Return on Equity, Percentage |
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10.25%
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| Public Utilities, Requested Rate Base, Amount |
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$ 1,900.0
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| Public Utilities, Requested Equity Capital Structure, Percentage |
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53.97%
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| NMPRC Proceeding - New Mexico 2016 Electric Rate Case |
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| Public Utilities, General Disclosures [Line Items] |
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| Public Utilities, Requested Rate Increase (Decrease), Amount |
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$ 41.4
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| Public Utilities, Requested Rate Increase (Decrease), Percentage |
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10.90%
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| Public Utilities, Requested Return on Equity, Percentage |
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10.10%
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| Public Utilities, Requested Rate Base, Amount |
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$ 832.0
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| Public Utilities, Requested Equity Capital Structure, Percentage |
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53.97%
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| Public Utility Commission of Texas (PUCT) | PUCT Proceeding - Appeal of the Texas 2015 Electric Rate Case Decision |
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| Public Utilities, General Disclosures [Line Items] |
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| Public Utilities, Approved Rate Decrease, Net of Rate Case Expenses |
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$ 4.0
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| Subsequent Event | PUCT Proceeding - Texas 2017 Electric Rate Case |
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| Public Utilities, General Disclosures [Line Items] |
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| Public Utilities, Revised Requested Rate Increase |
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$ 54.6
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| Public Utilities, Revised Requested Rate Increase, Percentage |
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5.80%
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| Public Utilities, Rate Case Expenses Addressed in Separate Proceeding |
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$ 4.4
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| Public Utilities, Revised Incremental revenue request |
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69.2
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| Transmission Cost Recovery Factory (TCRF) Rider | Subsequent Event | PUCT Proceeding - Texas 2017 Electric Rate Case |
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| Public Utilities, General Disclosures [Line Items] |
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| Public Utilities, Rider Conversion to Base Rates |
[1] |
$ 14.6
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| SPS | Southwest Power Pool (SPP) | SPP Open Access Transmission Tariff Upgrade Costs |
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| Public Utilities, General Disclosures [Line Items] |
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| Public Utilities, Billed Charges For Transmission Service Upgrades |
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$ 12.8
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| Public Utilities, Length of Payment Period Requested, In Years |
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5 years
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| Public Utilities, Monthly Billed Charges For Transmission Service Upgrades |
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$ 0.5
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